The best way to get Unity to listen is to cut the reproduction case down to the bare minimum: a project with Unity editor code that does only what is needed to cause the incorrect drawing.
We'll look into it further. Once Harald can reproduce it, he'll likely be able to say if we can implement a workaround.
@PeterBacall We have now pushed a potential bugfix for this issue.
New spine-unity 4.1 and 4.2-beta unitypackages are available for download:
https://esotericsoftware.com/spine-unity-download
Please let us know if the issue persists. Thanks for reporting!
For details see the following issue ticket:
EsotericSoftware/spine-runtimes2353
Harald
Unfortunately, tried with a fresh project and it's still there 
Edit: FWIW, in Unity 2023.2 (beta) the glitches have become very rare in the inspector, but area instead visible in the Scene view. (They are visible in the Scene View in 2023.1 too, but more rare). Really weird
@PeterBacall Terribly sorry, the download links on the English spine-unity download page failed to update and were pointing to an older package. Could you please try again with the updated download link, the correct package date containing the fix is 2023-08-29:
https://esotericsoftware.com/spine-unity-download
Harald
No worries! 2023-08-29 Doesn't seem to solve the glitches unfortunately :/
@PeterBacall Oh dear, sorry to hear. We can reproduce the issue on our end now at least. We will let you know once we've boiled the problem down to the problematic lines, we can then either hopefully provide a bugfix or report the bug to Unity.
@PeterBacall We could boil the issue down to a minimal reproduction project, it seems to be an issue with Unity. We have submitted a bugreport, hopefully it will be processed soon. We didn't receive a public ticket URL yet, but we will keep you informed as soon as we've received any updates from them.
Really good to know, thank you for keeping me posted and for reporting to Unity! Hopefully they will fix it soon, cheers! 
@PeterBacall Good news, we have just released new spine-unity 4.1 and 4.2-beta packages which should resolve the issue:
https://esotericsoftware.com/spine-unity-download
Big thanks go to user @Noeski here on this forum thread who discovered the fix!
FYI: Unity has created a public issue tracker ticket here:
https://issuetracker.unity3d.com/issues/visual-artifacts-appear-on-gameobject-and-in-the-editor-windows-when-gameobject-with-onscenegui-and-graphics-dot-drawmeshnow-is-moved-in-scene-view-on-macos
We've just informed them of the available fix (or workaround) and that if the checks are officially required that their docs should mention that.
Thanks for confirming, @PeterBacall, glad it's resolved!
